Dyeing



Patented Sept. 20, 1938 PATENT OFFICE DYEING Arthur J. Buchanan,Charlotte, N. 0., assignor, by mesne assignments, to Southern Dyestufl?Corporation, Charlotte, N. 0., a corporation of North Carolina .NoDrawing. Application June 19, 1936, Serial No. 86,078

2 Claims.

This invention relates to improvements in the art of dyeing with sulphuror sulphurized dyestuiis, andmore particularly to the production ofconcentrated solutions of such dyestufls, and it includes an improvedmethod. of making such solutions and the concentrated liquid sulphurizeddyestuffs resulting therefrom.

The sulphur or sulphurized dyestufis are generally speaking insoluble orsparingly soluble in water, but they are soluble in solutions of sodiumsulphide. In order to use these colors for dyeing purposes it isnecessary that they be made soluble and reduced. It is also importantthat these colors, after being dissolved and reduced; remain in solutionin the reduced state until the dyeing operation is complete.

The usual procedure in applying sulphur dyestufis to the fiber is todissolve and reduce the dyestuif with the aid of sodium sulphide and analkali such as sodium carbonate (soda ash). Other or additional reducingand solubilizing agents are sometimes used, either alone or With sodiumsulphide. The dissolved and reduced dyestuifs are subsequently dilutedand the cotton or other fabric or fiber immersed in the liquor, withsubsequent exposure to the air, etc. In dyeing cotton, for example, thecotton is commonly immersed in the dye liquor at a temperature near theboiling pointfor a suitable period of time, e. g., around one hour,followed by exposure to the air, etcl The preparation of dye liquors bydissolving and reducing the sulphurized dyestuffs with sodium sulphide,or with sodium sulphide and alkali, has certain well known and commonlyrecognized objections. The solutions are strongly alkaline and have thedisadvantage of removing the natural waxes and fats from v getable andanimal fibers and tend to leave the dyed material depleted in theseconstituents and with a harsh texture, unlike the softness of. textureof the original undyed material. Sodium sulphide, when used as areducing and dissolving agent for the sulphur colors, also has theobjection that it is readily oxidized by the air, thus tending to loseits value for keeping the dyestuff in a state of reduction and insolution. Sodium sulphide crystallizes from strong solutions and isconsequently dlfiicult to filter in high concentrations.

In an attempt to overcome the objections to the use'oi sodium sulphidein preparing reduced solutions of sulphur dyes, it has been proposed toreduce the high alkalinity of the dye solution,

for example, by the use of sodium bisulphite,

sodium hydrosulphite, glucose, salts of ammonia,

etc.; in which case the sulphur dyestufi is first dissolved and reducedin a highly alkaline solution of sodium sulphide and the alkalinity ofthe solution is subsequently reduced in an attempt to prevent orminimize injury to the fibers and other objectionable effects ofstrongly alkaline dye liquors.

The present invention is based upon the discovery that improved resultscan be obtained by the use of sodium disulphide (NazSz) instead of theordinary sodium sulphide NazS), as the dissolving and reducing agent forsulphurized dyestuffs.

The sodium disulphide has a greater reduction capacity or potential fora given unit of weight of strength than does the ordinary sodiumsulphide, due evidently to the greater amount of combined low valentsulphur which the sodium disulphide contains. Because of this it ispossible to use less of the sodium disulphide, with resulting beneficialresults in that there is less alkali present during the dyeing and,consequently, less saponification of the natural oils and waxes in thecotton; consequently the cotton is left in better condition, more nearlyapproximating natural, untreated cotton. It is possible also to produceshades which are brighter and fuller.

The use of sodium disulphide as a reducing agent has the added advantageor additional beneficial property that it is more stable towardoxidation than sodium sulphide; that is, it oxidizes more slowly andthis makes it a more desirable reducing agent for use in concentratedliquid dyestufi solutions which are marketed in that form.

Because of the advantageous properties which sodium disulphide possessesas a dissolving and reducing agent for sulphurized dyestuffs, highlyconcentrated dye solutions can be obtained by it use, which concentratedsolutions, because of their desirable properties, can advantageously bemarketed in that form.

The use of solutions of sodium disulphide for dissolving and reducingthe sulphurized dyestufls gives directly a solution of the reduced dyewhich is less caustic and more stable toward oxidation than when sodiumsulphide is used. The dyestuffs are readily kept in solution in a sodiumdisulphide solution and can be handled in a concentrated form. Such dyesolutions in general produce brighter and fuller shades, leaving thedyed material less harsh, and are less alkaline and of a lower pH valuethan solutions in sodium sulphide.

The new dye liquors or solutions can readily be used for dyeingvegetable fibers and fabrics and various artificial fibers, and also forprinting with the sulphur colors.

The method of application of the new dyestuif solutions is similar tothat with sodium sulphide solutionsbut with the use of materially lowertemperatures; since it has been found that the dyeing temperature can bereduced to around 150 F. with beneficial results, whereas it iscustomary to dye with sodium sulphide dye solutions at around 200 F.This use of a lower temperature involves not only a saving in time andcost of steam for heating but leaves the dyed cotton in a bettercondition.

I have also found that sodium disulphide can advantageously be employedin combination with sodium hydrosulphide, for example, using the sodiumdisulphide and sodium hydrosulphide in about equal proportions.

I have also found that a very small quantity of caustic soda may be usedwith the sodium di-- sulphide in which case the solution consists mainlyof sodium disulphide with a small amount of sodium sulphide.

I have also found that a very small quantity of caustic soda can be usedalong with the combination of disulphide and hydrosulphide; in whichcase the resulting composite solution contains sodium sulphide, sodiumhydrosulphide and sodium disulphide in varying proportions; but theresulting solution has a lower pH value than a sodium sulphide solutionand gives beneficial results, such as those above mentioned.

In making the new dye solutions, and in carrying out the new dissolvingand reduction process, the sodium disulphide is advantageously used in asolution of about 30% strength. Such a solution has a similar reductioncapacity to that of a solution of sodium'hydrosulphide of about the samestrength and considerably greater reduction capacity as compared with asodium sulphide solution of similar strength.

Highly concentrated solutions of sulphur colors can be prepared withrelative ease by dissolving and-reducing them in a solution of thesodium disulphide, and such highly concentrated solutions can be readilyfiltered, stored, transported and used. Solutions of similar highconcentration can similarlybe obtained by the use of admixed sodiumdisulphide and sodium hydrosulphide without or with the addition of avery small amount of caustic soda. When the sodium disulphide and sodiumhydrosulphide are used together with a small amount of caustic soda, thecomposite solution contains sodium sulphide, sodium hydrosulphide andsodium disulphide in varying proportions, e. g., with' the quantities ofeach that may be present in the composite solution varying from aminimum of around 10% up to a maximum of around In applying the sodiumdisulphide solution of the sulphurized dyestufi, the highly concentratedsolution can be handled much the same as sodium sulphide solutions ofthe dyestuffs, but with added advantages, such as the use of lowertemperatures and other advantages above mentioned. The concentratedsolution-can, for example, be diluted and the fiber or fabric dyedtherein and the dyestuif exhausted by the addition of sodium chloride,sodium sulphate, ammonium sulphate, sodium hydrosulphite, sodiumbisulphite, etc.

The sulphur dyestufls-are commonly marketed in the form of powders,usually admixed or diluted with more or less salt. Additional salt canbe added to aid in the dyeing operation and in exhausting the dye bath.It is common to add a small amount of soda ash or caustic soda to thedye bath; and such alkalies in small amount can be added in the practiceof the present process, although excellent results have been obtainedwithout such addition.

A particularly valuable application of the invention results from theuse of the moist presscake which is produced in the manufacture ofsulphur dyes, and without the drying of the dyes to produce a drypowder. Such moist dyestufl press-cakes are readily dissolved andreduced in a strong solution of sodium disulphite, and the resultingsolutions are particularly advantageous for use in the dyeing of textilefibers and fabrics. The use of the fresh moist press-cake and itsreduction and dissolving in the sodium disulphide solution eliminates orminimizes the changes which take place on drying of the press-cake toform dry dye powders. Solutions of the sulphurized dyes can be morereadily and advantageously prepared by using the moist presscake than byusing the dried dyestuffs which are produced by the drying of thepress-cake and which are generally less soluble and. less readilydissolved and reduced.

The new disulphide solutions of the sulphur dyes are readily preparedwithout the use of neutralizing agents such as have heretofore beenadded to sodium sulphide solutions to reduce their alkalinity. The newdye solutions can thus be prepared free or relatively free fromsulphites or bisulphites or other added neutralizing agents. Thesolutions are initially prepared by dissolving and reducing the sulphurdyes in the disulphide solution so that the solutions are initially ofmuch lower alkalinity and pH value than sodium sulphide solutions, andwith other advantages, such as those above mentioned.

The invention will be further illustrated by the following specificexamples, but it will be understood that the invention is not limitedthereto, since different sulphur or sulphurized dyestuffs can beemployed, and somewhat varying amounts and strengths of solutions ofsodium disulphide. The following examples are typical:

Example 1.- pounds of commercial sulphur black in the form of a drypowder having common salt admixed therewith for standardization aredissolved in from 100 to 200 pounds of a 30% solution of sodiumdisulphide at a temperature of about 80 C., and with accompanyingreduction of the dyestuflf. At this temperature and concentration thesolution can be readily filtered, decanted, etc., to remove insoluble,objectionable matter and a strong, stable solution of the dyestufl thusobtained suitable for storage and transportation or ready for use, bydilution, etc., in making a dye bath for dyeing textile fibers orfabrics. On cooling of the solution to ordinary temperatures thedyestufl remains in solution, and is ready for use, after dilution, etc.

Example 2.-100 pounds of commercial sulphur blue in the form of a drypowder having salt admixedtherewith for standardization are dissolved infrom 100 to 200 pounds of a 30% solution or sodium disulphide and theprocess is otherwise carried out in a manner similar to that describedin Example 1.

Example 3.--A sulphurized dyestufl, such as sulphur black or, sulphurblue, sulphur brown, etc., is used in the form of a moist press-cakecontaining e. 3. around 45% of water; and 100 75 pounds of thispress-cake is dissolved in from 100 to 200 pounds of a 30% solution ofsodium disulphide. The dissolving and reduction take place more readilyin this case than with the dry sulphurized dye powder, and somewhatimproved dye solutions are thus obtained without the necessity ofisolating and drying the sulphur dye and subsequent handling of dry dyepowders with their well known objections due to dusting, and theirritating or toxic effect of the dust, etc.

The following examples illustrate the production of concentratedsolutions of sulphurlzed dyestufi's with a composite solution 01' sodiumdisulphide and sodium hydrosulphite either without or with the additionof a small amount of caustic soda, in which case the composite solutionscontain sodium disulphide, sodium sulphide and sodium hydrosulphide.

Example 4.--100 pounds of commercial sulphur black in the form of a drypowder having commonsalt admixed therewith for standardization aredissolved in from 100 to 200 pounds of a composite solution of sodiumhydrosulphide and sodium disulphide containing approximately equalamounts of the hydrosulphide and disulphide in amount suflicient to givea solution of about 30% strength and at a temperature of about 80 C.-,with accompanying reduction of the dyestuff. At this temperature andconcentration the solution can be readily filtered, decanted, etc., toremove insoluble, objectionable matter and a strong, stable solution ofthe dyestufl thus obtained suitable for storage and transportation orready for use, by dilution, etc., in making a dye bath for dyeingtextile fibers or fabrics. On cooling of the solution to ordinarytemperatures the dyestuii remains in solution, and is ready foruse,after dilution, etc.

Example 5.A sulphurlzed dyestuii', such as sulphur black or sulphurblue, etc., is used in the form of a moist press-cake containing e. g.,around of water; and 100 pounds ot'this press-cake is dissolved, in from100 to 200 pounds of a 30% solution, containing approximately equalproportions of sodium hydrosulphide, sodium sulphide and sodiumdisulphide. The dissolving and reduction take place more readily in thiscase than with the dry sulphurlzed dye powder, and somewhat improved dyesolutions are thus obtained without the necessity oi isolataboveexamples are typical and may be used:

without or with additional substances, by dilution, etc., in making dyeliquors or dye baths for dyeing and printing textile fibers and fabric-aWhere the sodium disulphide is used in admixture with sodiumhydrosulphide, the proportions of disulphide and hydrosulphide can bevaried, as above indicated. Similarly, where a .small amount of causticsoda is used in addition to the sodium disulphide and sodiumhydrosuiphide, the resulting composite solution of sodium sulphide,sodium disulphide and sodium hydrosulphide may also vary in itsproportions, as previously pointed out.

It' is one 01 the advantages oi the new composite dye liquor, as well asan advantage of the dye liquor made with sodium disulphide alone, thatlower temperatures can be used in the dyeing process than with thesodium sulphide solutions commonly used.

The new composite dyestuif solutions, produced by reducing thesulphurized dyestuffs with the sodium disulphide'red'ucing agent, orwith the composite reducing agent containing sodium disulphide, areadvantageously marketed commercially as concentrated, reduced dyestuiIsolutions ready for the dyer to use.

Various sulphur dyestuifs and various shades of sulphurlzed dyestuffscan be used in making the new dyestufi solutions; for example, suchsulphurlzed dyestuilfs and such shades of sulphurized dyestuifs asblack, blue, tan, yellow, green, etc., sulphurized dyes.

It will be evident that the above examples can be varied, e. g., in theparticular sulphurlzed dyestuil employed and in the particularcomposition of the reducing solution, particularly where a compositereducing solution is used.

I claim:

1.. Liquid sulphur dye being a concentrated, fliterable solution ofsulphurlzed dyestufi dissolved and reduced in a-concentrated compositesolution of sodium sulphide, sodium disulphide and sodium hydrosulphide,in which the sodium sulphide, sodium disulphide and sodium hydrosulphideare present in approximately equal amounts, said dye solution containingapproximately from 18% to of the sulphurized dyestuii', and beingcharacterized by improved stability toward oxidation and by relativelylow pH value. v

2. Liquid sulphur dye, being a concentrated, filterable solution ofsuiphurized dyeatufl' dissolved and reduced in a concentrated compositesolution of sodium disulphide and sodium hydrosulphide, in which thesodium disulphide, and sodium hydrosulphide are present in approximatelyequal amounts, said dye solution containing approximately from 18% to50% of the sulphurlzed dy'estufi, and being characterized by improvedstability toward oxidation and by relatively low pH value.

. ARTHUR. J. BUCHANAN.

